Water source heat pumps are used to provide temperature regulation for interior spaces. A water source heat pump makes use of the ground as a heat reservoir by either storing heat removed from interior spaces in the ground or removing heat from the ground and applying it to the interior spaces. Such a heat pump is referred to as an earth coupled heat pump. An earth coupled heat pump accesses the ground-based heat reservoir through a piping installation which is buried in the ground and through which liquid fluid, such as water or a water and an antifreeze solution, circulates.
The piping installation of an earth coupled heat pump may be configured in either a series arrangement, where all of the fluid travels through the same pipe, or a parallel arrangement, where the fluid travels through different branches in the pipe. A parallel piping installation includes a supply header, a return header, and a plurality of parallel branches connected between the two headers.
Any piping installation is susceptible to fluid circulation problems caused by air trapped within the pipes. Air is typically trapped within the various pipes during the installation process. However, in a series arrangement, any trapped air can be removed by thorough purging of the piping system. Trapped air presents a more serious problem in a parallel piping installation where purging may not be able to remove all of the air. Inadequate air removal is common because the air follows the path of least resistance and eventually congregates in one branch, typically the last branch. Because of the head loss that it would take to move the air bubble out of the affected branch, the fluid in the piping installation follows the path of least resistance and splits its flow between the remaining branches. This flow pattern results in a loss of use of the affected branch and reduces the overall system efficiency accordingly.
In the prior art, as disclosed by U.S. Pat. No. 4,538,673, the trapped air is passed from the supply header to the return header through fittings which nominally by-pass each parallel branch. Each fitting has a small orifice for letting air pass directly from the supply header to the return header. This type of arrangement requires close physical proximity between the supply and return headers resulting in thermal interference between the headers and some loss of system efficiency. In addition, the headers may undergo unnecessary stress due to incorrect pipe alignment or pipe memory mismatch.